Skip to content
Fencer Vulns
high 8.6

CVE-2021-32777 json

Incorrect concatenation of multiple value request headers in ext-authz extension

published 2021-08-24 5 y ago modified 2026-09-08 2 mo ago also BIT-envoy-2021-32777 , EUVD-2021-19541 , GHSA-6g4j-5vrw-2m8h

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.3%
EPSS 3.3% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known

Summary

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions when ext-authz extension is sending request headers to the external authorization service it must merge multiple value headers according to the HTTP spec. However, only the last header value is sent. This may allow specifically crafted requests to bypass authorization. Attackers may be able to escalate privileges when using ext-authz extension or back end service that uses multiple value headers for authorization. A specifically constructed request may be delivered by an untrusted downstream peer in the presence of ext-authz extension. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to the ext-authz extension to correctly merge multiple request header values, when sending request for authorization.

Patch / fix

  • bitnami envoy 1.16.5, 1.17.4, 1.18.4, 1.19.1
  • envoyproxy envoy 1.16.5, 1.17.4, 1.18.4
  • servicemesh service mesh 1.1 1.1.17-3.el8
  • servicemesh-mixc service mesh 1.1 1.1.17-3.el8
  • servicemesh-mixs service mesh 1.1 1.1.17-3.el8
  • servicemesh-proxy service mesh 1.1 1.1.17-2.el8
  • servicemesh-galley service mesh 1.1 1.1.17-3.el8
  • servicemesh-citadel service mesh 1.1 1.1.17-3.el8
  • servicemesh-istioctl service mesh 1.1 1.1.17-3.el8
  • servicemesh-pilot-agent service mesh 1.1 1.1.17-3.el8

red hat advisories RHSA-2021:3273RHSA-2021:3272

  • istio Arch Linux 1.11.1-1

arch linux advisories AVG-2321

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-32777 updated cvss 8.3

envoyproxy/envoy: HTTP request with multiple value headers can bypass authorization policies

  • Red Hat OpenShift Service Mesh 1.1 servicemesh-proxy 1.1.17-2.el8
    fixed: vendor fix RHSA-2021:3273
  • Red Hat OpenShift Service Mesh 2.0 servicemesh-proxy 2.0.7-3.el8
    fixed: vendor fix RHSA-2021:3272
  • Red Hat OpenShift Service Mesh 1.1 servicemesh 1.1.17-3.el8, servicemesh-mixc 1.1.17-3.el8, servicemesh-mixs 1.1.17-3.el8, servicemesh-galley 1.1.17-3.el8, servicemesh-citadel 1.1.17-3.el8, servicemesh-istioctl 1.1.17-3.el8, +3 more Red Hat OpenShift Service Mesh 2.0 servicemesh 2.0.7-3.el8, servicemesh-mixc 2.0.7-3.el8, servicemesh-mixs 2.0.7-3.el8, servicemesh-istioctl 2.0.7-3.el8, servicemesh-pilot-agent 2.0.7-3.el8, servicemesh-pilot-discovery 2.0.7-3.el8
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.33% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
NVD 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

Affected packages

ecosystem package affected fixed in
bitnami envoy
>=1.16.0, <1.16.5
>=1.17.0, <1.17.4
>=1.18.0, <1.18.4
>=1.19.0, <1.19.1
1.16.5
1.17.4
1.18.4
1.19.1

Affected products

  • envoyproxy envoy

Classification

Weakness
  • CWE-551 Incorrect Behavior Order: Authorization Before Parsing and Canonicalization
  • CWE-863 Incorrect Authorization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.